Electronic speedometer/odometer with interchangeable calibrating means for accommodating a plurality of vehicle tire sizes

ABSTRACT

This invention relates to an electronic speedometer/odometer responsive to pulses from a wheel speed sensor which may include a speedometer circuit and an ammeter for indicating speed with provision for interchangeably inserting calibrating resistors in the meter circuit for establishing a meter response in accordance with the vehicle tire size, and an odometer programmable circuit connected to an odometer with provision for interchangeably inserting program circuits for establishing the response of the odometer selected in accordance with the vehicle tire size. Preferably, the meter calibration resistor and the odometer program circuit are mounted in a single interchangeable unit.

United States Patent 1191 [11] 3,7393% Miller et al. June 12, 1973 [54]agi fggi fiffgggfi gfigfiggg FOREIGN PATENTS OR APPLICATIONS MEANS FORACCOMMODATING A 968,008 8/1964 Great Bntam 324/171 PLURALITY OF VEHICLETIRE SIZES Primary Examiner Michael J. Lynch [75] Inventors: Roger L.Miller, Ann Arbor; Robert Atmmey Hamess, Dickey & pierce S. Podlewslri,Jackson, both of Mich.

[73] Assignee: fielslcy Hayes Company, Romulus, [57] ABSTRACT 1c Thisinvention relates to an electronic speedometer/o- Flledi 1971 dometerresponsive to pulses from a wheel speed sen- [21] Appl No; 111,399 sorwhich may include a speedometer circuit and an ammeter for indicatingspeed with provision for interchangeably inserting calibrating resistorsin the meter [52] U.S. Cl. 324/166, 324/171 circuit for establishing ameter response in accordance [5 Cl. n; the vehi le tire size and anodometer rogramma- [58] new of Search 324/168 1711 ble circuit connectedto an odometer with provision for 324/173, 174, 175; interchangeablyinserting program circuits for establishing the response of the odometerselected in accor- [56] References Cited dance with the vehicle tiresize. Preferably, the meter UNITED STATES PATENTS calibration resistorand the odometer program circuit 3,358,230 12/1967 Wiley 324/171 aremounted in a Single interchangeable unit 3,477,022 11/1969 LeMasters324/171 3,441,943 4/1969 McCue 324/71 18 Clam, 6 Drawmg 22 311;? I 4/ /452 4. 07 //4 54/12/1712; 2 5 5 7 e: $57 i fiiii? j;f;gg

ELECTRONIC SPEEDOMETER/ODOMETER WITH INTERCHANGEABLE CALIBRATING MEANSFOR ACCOMMODATING A PLURALITY OF VEHICLE TIRE SIZES BACKGROUND ANDSUMMARY OF THE INVENTION The trucking industry uses a substantial rangeof tire sizes on their vehicles to meet the special requirements of thatindustry. By way of example, the tire sizes used by the truckingindustry may vary so as to provide from 460 wheel revolutions per mileto 630 wheel revolutions per mile.

The present invention provides a speedometer/odometer which canaccomodate a wide range of tire sizes using only a single basicapparatus which is calibrated in accordance with a particular tire sizeby an interchangeable unit. In general, the speedometer/odometer of thisinvention is responsive to a wheel speed sensor and includes anindicator for providing an indication of vehicle velocity and/oraccumulated distance traveled by the vehicle in combination with acalibration unit for affecting the indication in accordance with thetire size of the vehicle. An exemplary embodiment ofspeedometer/odometer according to the present invention utilizes aspeedometer circuit, preferably an integrated circuit, which receivespulses from a wheel speed sensor and provides an output signal having anaverage current level indicative of the number of pulses generated bythe wheel speed sensor per unit time which is received by an ammeter.Terminal means are provided in the meter circuit for insertion of aresistor of selected resistance value, or no resistor at all, tocalibrate the meter in accordance with the tire diameter. Thespeedometer/odometer is also provided with an odometer circuit which mayreceive either the pulses from the wheel speed sensor or the outputsignal of the speedometer circuit to provide a signal representative ofthe distance traveled by the vehicle. The odometer circuit has means forselectively programming the circuit so as to control its output signalwith respect to a given input signal so that it provides a signal inaccordance with the actual distance traveled by the vehicle. The outputsignal of the odometer is received by an operatively associated odometerto accumulatively register the distance traveled by the vehicle. Morespecifically, the odometer circuit may be a programmable integratedcircuit which receives pulses from the speedometer circuit and dividesthose pulses by a divisor in accordance with the tire size of thevehicle to yield output pulses which are reduced in number. The divisoris established by a program circuit which is interchangeably connectableto the odometer circuit. The output pulses of the odometer circuit maybe received by an odometer driver for driving a stepping motor which inturn operates an odometer register through a reduction gear. Preferably,both the resistor for calibrating the speedometer circuit and theprogram circuit for establishing the divisor of the odometer circuit aremounted in a single detachable and interchangeable plug-in unit whichcan be connected to the speedometer/odometer assembly after theconstruction of the assembly.

In view of the foregoing description of an exemplaryspeedometer/odometer assembly according to this invention, it will beappreciated that only a single basic speedometer/odometer unit need bedesigned and constructed for a wide variety of vehicle applicationsthereby simplifying the manufacturing and inventory requirements forsupplying the trucking industry with speedometer/odometer units.Moreover, the speedometer/odometer units of this invention are capableof relatively fine matching to a vehicle application and consequently, ahigh level of accuracy is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of anexemplary speedometer/odometer apparatus according to this invention;

FIG. 2 is a perspective illustration of the rear portion of a housingfor an exemplary speedometer/odometer apparatus according to thisinvention showing a calibration plug;

FIG. 3 is a circuit diagram of a portion of the speedometer circuit ofFIG. 1 including a wheel speed sensor, a speedometer circuit, a speedindicating meter, and a calibration resistor for the speedometercircuit;

FIG. 4 is a circuit diagram of another portion of the speedometercircuit of FIG. 1 including an odometer circuit with programming circuitterminals;

FIG. 5 is a circuit diagram of an exemplary programming circuit for theodometer circuit of FIG. 4; and

FIG. 6 is a circuit diagram yet another portion of thespeedometer/odometer circuit of FIG. 1 including an odometer steppingmotor driving circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a schematicdiagram of an exemplary speedometer/odometer 10 is illustrated. The

speedometer/odometer 10 operates in conjunction with a wheel speedsensor 12, which may be one of the wheel speed sensors of a brakeantiskid system, consisting of a rotor 14 and a stator 16. Wheel speedsensors of this type are well known to the art and therefore a detaileddescription thereof will not be provided. By way of example, the wheelspeed sensor 12 may provide electrical pulses for each wheel revolutionon an output line 18. Consequently, with appropriate calibration, thenumber of pulses may be made representative of the distance traveled bya vehicle whereas the rate of pulse generation may be maderepresentative of the speed of the vehicle. The pulses along line 18 aretransformed by a speedometer circuit 20 into corresponding pulses ofpredetermined constant width and amplitude appearing at output lines 22and 24. The pulses on output line 22 are received by a speedometer meter26 which may be a milliammeter which measures the average current levelon line 22, and consequently, the rate of repetition of the pulses online 22. An odometer circuit 28 receives the train of regulated pulsesfrom the speedometer circuit 20 on line 24 and divides those pulses by apredetermined divisor to yield a numerically reduced train of pulses online 30. The pulses on line 30 are delivered to an odometer driver 32which provides an output signal on line 34 of sufficient strength todrive a stepping motor 36 which is mechanically coupled through areduction gear 38 to an odometer indicator 40 within a housing 42 forthe speedometer/odometer 10 as seen in FIG. 2. The speedometer 26 andthe odometer circuit 28 are calibrated for different tire sizes using aplug-in calibration unit 44 which can be seen attached to the back ofthe speedometer/odometer housing 42 by a wing nut 46 as shown in FIG. 2.To this end, the housing 42 carries terminals which correspond toterminals on the calibration unit 44 which may be of any appropriatetype.

In FIG. 3, an exemplary embodiment of a speedometer circuit 20 is shown.The speedometer circuit 20 receives battery positive terminal voltage ata supply terminal 48. It is further connected to the negative terminalof the battery at a terminal 541. The input circuit has a diode D1 isconnected to the supply terminal 48 to prevent the destruction of thecircuit in the event of a reverse polarity connection, a resistor R1 forcurrent limiting a filter capacitor C1, and a voltage regulating a zenerdiode D2 so as to provide a filtered regulated voltage on a line 52. Theregulated voltage is delivered to a supply terminal 14 of a firstintegrated circuit ICl (herein, underlined terminals designate ICterminals). The integrated circuit 1C1 may be a model SW780 manufacturedby Stewart-Warner Microcircuits, Inc., 730 E. Evelyn Avenue, Sunnydale,California. The terminals are numbered on 1C1 in FIG. 3 in accordancewith the standard numbering practice for the above Model SW780.

The input train of pulses on line 18 from the sensor 12 is deliveredthrough a DC blocking capacitor C3 and a current limiting resistor R3 toan input terminal 8 of lCl. The lCl is provided with a timing capacitorC2 connected between its terminals 9 and 11 and pulse-width establishingresistor R4 connected between its terminals 9 and 3. Additionally,terminals 1 and 4 are interconnected in accordance with the standardpractice recommended by the manufacturer for the above integratedcircuit. The integrated circuit lCl provides output pulses at terminal12 corresponding with the input pulses on line 18 which are received bylines 22 and 24. The output pulses have preselected constant widths andamplitudes. Line 22 has a resistor R2 for initial calibration of themeter 26 at the time of assembly. The line 22 is connected to thespeedometer meter 26 which may be a milliammeter having a zero to lmilliampere rating. The meter circuit is completed through a resistorR5, and under selected conditions, through a calibration resistor RCwhich is connected in parallel with the resistor R between the meter 26and negative battery potential at terminal 50. It can be seen that theresistors R5 and RC determine the current flow through the meter 26, andaccordingly, establish the amplitude of the response of the meter 26 tothe pulse rate from the wheel speed sensor 12.

The meter reading of the speedometer meter 26 is established inaccordance with wheel size by the provision of the calibration resistorRC, preferably carried by the calibration plug 44. In this regard, itwill be appreciated that smaller wheel sizes have a greater number ofrotations per mile, and accordingly, the resistance of the calibrationresistor RC is selected to be relatively larger. For the smallest wheelsizes, the resistor R5 which is in parallel with the calibrationresistor RC may be established so that the speedometer 26 is correctlycalibrated. For increasing wheel sizes calibration resistors RC ofdecreasing resistance values are inserted in parallel with resistor R5so as to increase the sensitivity of the speedometer meter 26.

In FIG. 4, a circuit diagram of an odometer circuit 28 is illustrated.The odometer circuit 28 receives pulses from the speedometer circuit online 24 at the base of a transistor 01 through a current limitingresistor R9. The input of an integrated circuit 1C2 is connected to thecollector of the transistor Q1 at terminal 58. The

terminal 58 is maintained near positive potential when the transistor 01is non-conductive and is pulled down to near negative battery potentialwhen the transistor Q1 is conductive to deliver a pulse to the input of1C1 upon each pulse received at the base of the transistor 01. To thisend, a resistor R8 is connected between the positive supply conductor.54 and the terminal 58 to provide a voltage drop from positive supplypotential when the transistor 01 conducts. The integrated circuit 1C2may be a I-ICTRO507 (l-IRM2034), seven-stage programmable countermanufactured by the Newport Beach Division of the Hughes AircraftCompany, Newport Beach, California. Using the nomenclature for theaforementioned HCTR0507 (Hills [2034), the [C2 has, in thecounterclockwise direction, an input terminal 7 connected to thecollector of transistor Q1 at 58, a reset terminal 8, a positive supplyterminal 10 connected to regulated supply voltage line 54, a divisorterminal 1 1 representing a divisor of 64, a divisor terminal 12representing a divisor of 32, a divisor terminal 13 representing adivisor of 16, negative supply terminals 14 and 1, a divisor terminal 2representing a divisor of 8, a divisor terminal 3 representing a divisorof 4, a divisor terminal 4 representing a divisor of 2, and a divisorterminal 5 representing a divisor of 1. As can be seen in the drawing,each of the divisor terminals is provided with a gating diode indicatedas D3-D8 and D10 and the reset terminal 8 is provided with a gatingdiode D9. The divisor terminal 11 representing a divisor of 64 isconnected to one terminal 60 of a resistor R7. The other terminal of theresistor R7 is connected to the negative battery voltage terminal 56.The reset terminal 8 is also connected through its associated gatingdiode D9 to the terminal 60. The aforementioned IC2 is operative suchthat the device will count while the terminal 8 is maintained at apredetermined positive level and will reset when terminal 8 goesnegative. Consequently, a positive potential maintained at terminal 60will establish a counting condition in the integrated circuit IC2whereas a negative potential impressed on the terminal 60 will restartthe counting sequence of the integrated circuit 1C2. The potential atthe terminal 60 is controlled between the operative positive andnegative levels in accordance with the programming established for theintegrated circuit IC2.

The divisor terminals 5-2 and 13-12 representing the divisors 1, 2, 4,8, 16 and 32 are connected through the respective gating diodes tocorresponding programming terminals Q1, Q2, Q4, Q8, Q16 and Q32. Afeedback terminal 62 is also provided which is connected to the terminal60 of the resistor R7. The programming terminals and the feedbackterminal 62 are accessible for connection to the calibration plug 44.

In the operation of the integrated circuit 1C2, each of the divisorterminals initially are positive until the number of pulses received atthe input terminal equals the respective divisor number for the divisorterminal at which time the divisor terminal will go negative for a likenumber of pulses, and again positive for a like number in sequence.Presuming that the odometer circuit 28, as shown in FIG. 4 without anyconnections at the programming terminals, has been reset by a negativepulse at the reset terminal 8, and thereafter, pulses are supplied tothe input terminal 7 from terminal 58, terminal 11 representative of thedivisor 64 will remain positive until the sixty-fourth pulse is receivedat the input terminal 7 at which time terminal 11 will go negativepulling down terminal 60 so as to correspondingly pull down the resetterminal 8 through the gating diode D9 to reset the integrated circuit1C2. Accordingly, the countup to 64 will begin anew. Since the remainingdivisor terminals are not connected to terminal 60 as shown in FIG. 4,they do not effect the resetting of ICZ. If, for example, the programterminals are connected to the feedback terminal 62 in a manner shown inFIG. 5, the count required to reset the integrated circuit IC2 will bechanged accordingly. With reference now to FIG. 5 in which a circuitdiagram is shown of an exemplary programming circuit for the calibrationplug shown in FIG. 1, it can be seen that program terminals Q16, Q8, andQ4 are connected to the feedback terminal 62 to provide a combinedprogrammed divisor of 92. With that programming arrangement, 92 inputpulses at input terminal 7 are required before all of the divisorterminals connected through the terminal 60 fall to the lower potentialso as to reset 1C2 at terminal 8. More particularly, terminal 11representative of the divisor 64 will drop to the lower potential after64 input pulses at which time programming terminals Q16, Q8 and Q4 willall be at positive potential because of their numerical relationshipwith 64. It will be appreciated that during the initial count up to 64,program terminal Q16 has cycled twice through high potential and lowpotential values, programming terminal Q8 has cycled four times, andprogramming terminal Q4 has cycled eight times. After an additional 16input pulses, the programming terminal Q16 will go negative, however,the terminal 60 will remain positive since Q8 and Q4 are not positive.After additional 8 input pulses, Q8 will go negative but the terminal 60will still remain positive since Q4 has become positive. After a stilladditional four input pulses, a total of 92 input pulses, Q4 will gonegative at which time all of the divisor terminals connected toterminal 60 will be negative so as to allow the reset terminal 8 to gonegative to reset the device. If desired, divisor terminal 11representative of divisor 64 may be brought out to the program terminalsand likewise programmed, however, for most applications a minimumdivisor of 64 will be required. When the integrated circuit IC2 isreset, terminal 11 representative of divisor 64 goes positive whichproduces a pulse at a coupling capacitor C4 which is connected toterminal 11. The pulse from capacitor C4 is transmitted to the odometerdriver 32 on line 30.

It will be understood that the above integrated circuit 1C2 is but oneexample of known programmable circuits, some using differing program andoperational schemes, which may be suitably used in thespeedometer/odometer of this invention.

With reference now to FIG. 6, an exemplary odometer driver circuit 32 isillustrated. The odometer driver circuit 32 is connected to a source ofunregulated positive potential by a line 64, also illustrated in FIG. 3.It is also connected to the negative terminal battery voltage throughterminal 66. The odometer driver 32 receives the output pulses of theodometer circuit 28 on line 30 at the base of transistor 03 such thattransistor Q3 is turned on each time a pulse is received from line 30.The collector-emitter circuit of transistor 03 is connected in serieswith the winding 68 of the stepping motor 36 for energizing the windingswhen O3 is on. The collector of O3 is connected at point 70 to acapacitor C6 which is in turn connected to the base of a transistor 02through a resistor R11. A capacitor C5 and a resistor R111 is connectedbetween the emitter and base of the transistor Q2 while the collector isconnected to negative battery potential through a voltage dividerconsisting of resistors R12 and R13 which has its midpoint connected tothe base of transistor Q3. When transistor Q3 is turned on, point. 70 ispulled down to near negative battery potential. Since the charge acrossthe capacitor C6 cannot change instantaneously, the opposite terminal ofcapacitor C6 is also brought down to near the negative batterypotential. Accordingly, a voltage drop occurs through the resistors R10and R11 which lowers a potential at the base of the transistor Q2 toturn transistor Q2 on thereby connecting the positive supply potentialto the base of the transistor Q3 through the emitter-collector circuitof transistor Q2 and resistor R12 to hold the transistor Q3 on after theinput pulse from the odometer circuit 28 on line 30 dissipates. As thecapacitor C6 charges, the potential at the base of transistor Q2 willrise until transistor Q2 turns off turning off transistor Q3. Theelapsed time between turning on of the transistor Q3 and the turning offof the transistor 03 by the transistor Q2 is determined by the timeconstant established by the capacitor C6 and the resistors R10 and R11.The transistor Q3 remains in conduction for a sufficient time to allowthe stepping motor 36 to rotate through one increment. A diode D11 isconnected across the winding 68 of the steppingmotor to prevent negativetransients when the stepping motor 36 turns off. The stepping motor, aspreviously stated, is connected to an odometer dial through a mechanicalreduction gear arrangement.

By way of illustration, if a wheel speed sensor providing 120 pulses perwheel revolution is used in combination with a stepping motor andreduction gear assembly providing a mechanical reduction ratio of 600 tol on a vehicle having a tire size providing 504 revolutions per mile, adivisor of 92 input pulses per output pulses will provide an appropriateoverall ratio.

In view of the foregoing description, it will be appreciated that aspeedometer/odometer combination is provided which is ideally suited foruse where a wide variety of tire sizes must be accomodated such as inthe trucking industry. The present invention enables only one basicspeedometer/odometer unit to be designed, manufactured and stocked whilethe variations to accomodate different tire sizes are provided in theform of a calibration plug which is relatively simple and inexpensive tomanufacture since it contains only a single resistor and a small numberof connecting or patching lines. Accordingly, these plugs can be stockedwith a minimum amount of inventory dollar value and space giving a widerange of flexibility to the use of the speedometer/odometer unitsaccording to this invention.

While it will be apparent that the teachings herein are well calculatedto each one skilled in the art the method of making preferred embodimentof this invention, it will be appreciated that the invention issusceptible to modification, variation and change without departing fromthe proper scope of meaning of the subjoined claims.

What is claimed is:

1. For a vehicle having a wheel with a tire of a predetermined size anda sensor providing a signal having a frequency representative of therate of rotation of the vehicle wheel; an apparatus for indicatingvehicle speed and the distance traveled by the vehicle compris- In Ipeed indicating means responsive to said sensor signal for providing aspeed indication;

odometer means including frequency dividing circuit means responsive tosaid sensor signal'for providing an output signal having a frequencyrepresentative of said sensor signal frequency divided by a quotient,said odometer means utilizing said dividing circuit means to provide anindication of the distance traveled by the vehicle; and

Calibrating means receiving means operatively associated with each ofsaid speed indicating means and said odometer means; and

unitary calibrating means being interchangeably received by saidcalibrating means receiving means for calibrating both said speedindicating means and said odometer means in accordance with saidpredetermined tire size, said unitary calibrating means includingspeedometer calibrating means for establishing the responsiveness ofsaid speed indicating means to said sensor signal and odometercalibrating means for changing said quotient of said frequency dividingcircuit means.

2. An apparatus according to claim 1 wherein said speed indicating meansand said odometer means responds to an electrical signal from the sensorrepresentative of the rotation of said vehicle wheel.

3. An apparatus according to claim 2 wherein said speed indicating meansand said odometer means responds to a predetermined number of electricalpulses from the sensor for each rotation of said vehicle wheel.

4. An apparatus according to claim 1 wherein said speedometercalibrating means includes a resistor adapted to establish theresponsiveness of said speed indicating means to said sensor signal.

5. An apparatus according to claim 4 wherein said speed indicating meansis a meter and said resistor is in a circuit for said meter establishingthe responsiveness thereof. a

6. An apparatus according to claim 1 wherein said odometer calibratingmeans includes a circuit program for said odometer means.

7. An apparatus according to claim 6 wherein said circuit program is inthe form of a circuit having conductors for establishing preselectedcircuit connections with said calibrating means receiving meansfor-establishing said quotient of said dividing circuit means.

8. An apparatus according to claim 1 wherein said dividing circuit meansis programmable to establish said quotient in accordance with the sizeof said tire.

9. An apparatus according to claim 8 wherein said odometer calibratingmeans is a program in the form of a circuit having conductors forestablishing preselected circuit connections adapted to be operationallycooperative with said dividing circuit means for establishing saidquotient.

10. An apparatus according to claim 9 wherein said odometer meansfurther includes a stepping motor for providing said odometer indicationin accordance with said dividing circuit means output signal.

1 1. An apparatus according to claim 10 wherein said .odometer meansincludes driving circuit means receiving said dividing circuit meansoutput signal for providing electrical pulses to said stepping motormeans which provide one rotational step of said stepping motor upon oneoutput pulse of said driving circuit means.

12. For a vehicle having a wheel with a tire of a predetermined size; anapparatus for indicating vehicle speed and the distance traveled by thevehicle comprising:

a sensor providing a predetermined number of pulses for each rotation ofthe vehicle wheel regardless of tire size so that the frequency of saidsignal is representative of the rate of rotation of the vehicle wheel;

speed indicating means responsive to said sensor signal for providing aspeed indication;

odometer means including frequency dividing circuit means responsive tosaid sensor signal for providing an output signal having a frequencyrepresentative of said sensor signal frequency divided by a quotient,said odometer means utilizing said dividing circuit means to provide anindication of the distance traveled by the vehicle, and

calibrating means receiving means operatively associated with each ofsaid speed indicating means and said odometer means; and

unitary calibrating means being interchangeably received by saidcalibrating means receiving means for calibrating both said speedindicating means and said odometer means in accordance with saidpredetermined tire size, said unitary calibrating means includingspeedometer calibrating means for establishing the responsiveness ofsaid speed indicating means to said sensor signal and odometercalibrating means for changing said quotient of said frequency dividingcircuit means.

13. An apparatus according to claim 12 wherein said speedometercalibrating means includes a resistor adapted to establish theresponsiveness of said speed indicating means to said sensor signal.

14. An apparatus according to claim 13 wherein said indicating means isa meter with said resistor in a circuit for said meter establishing theresponsiveness thereof.

15. An apparatus according to claim 12 wherein said calibrating means isa program for said apparatus.

16. An apparatus according to claim 21 wherein said program is in theform of a circuit for establishing preselected circuit connections withsaid means operatively associated with said indicating means forestablishing the responsiveness of said indicating means to said sensorsignal in accordance with said program.

17. An apparatus according to claim 12 wherein said means operativelyassociated with said indicating means includes a circuit for receivingpulses representative of the rotation of said vehicle wheel which isadapted to provide output pulses which are representative of the inputpulses divided by a divisor, said circuit being programmable toestablish said divisor in accordance with the size of said tire, saidindication being in accordance with said programmable circuit outputpulses.

18. An apparatus according to claim 17 wherein said calibrating means isa program in the form of a circuit having preselected circuitconnections adapted to be operationally cooperative with saidprogrammable circuit for establishing said divisor.

1. For a vehicle having a wheel with a tire of a predetermined size anda sensor providing a signal having a frequency representative of therate of rotation of the vehicle wheel; an apparatus for indicatingvehicle speed and the distance traveled by the vehicle comprising: speedindicating means responsive to said sensor signal for providing a speedindication; odometer means including frequency dividing circuit meansresponsive to said sensor signal for providing an output signal having afrequency representative of said sensor signal frequency divided by aquotient, said odometer means utilizing said dividing circuit means toprovide an indication of the distance traveled by the vehicle; andCalibrating means receiving means operatively associated with each ofsaid speed indicating means and said odometer means; and unitarycalibrating means being interchangeably received by said calibratingmeans receiving means for calibrating both said speed indicating meansand said odometer means in accordance with said predetermined tire size,said unitary calibrating means including speedometer calibrating meansfor establishing the responsiveness of said speed indicating means tosaid sensor signal and odometer calibrating means for changing saidquotient of said frequency dividing circuit means.
 2. An apparatusaccording to claim 1 wherein said speed indicating means and saidodometer means responds to an electrical signal from the sensorrepresentative of the rotation of said vehicle wheel.
 3. An apparatusaccording to claim 2 wherein said speed indicating means and saidodometer means responds to a predetermined number of electrical pulsesfrom the sensor for each rotation of said vehicle wheel.
 4. An apparatusaccording to cLaim 1 wherein said speedometer calibrating means includesa resistor adapted to establish the responsiveness of said speedindicating means to said sensor signal.
 5. An apparatus according toclaim 4 wherein said speed indicating means is a meter and said resistoris in a circuit for said meter establishing the responsiveness thereof.6. An apparatus according to claim 1 wherein said odometer calibratingmeans includes a circuit program for said odometer means.
 7. Anapparatus according to claim 6 wherein said circuit program is in theform of a circuit having conductors for establishing preselected circuitconnections with said calibrating means receiving means for establishingsaid quotient of said dividing circuit means.
 8. An apparatus accordingto claim 1 wherein said dividing circuit means is programmable toestablish said quotient in accordance with the size of said tire.
 9. Anapparatus according to claim 8 wherein said odometer calibrating meansis a program in the form of a circuit having conductors for establishingpreselected circuit connections adapted to be operationally cooperativewith said dividing circuit means for establishing said quotient.
 10. Anapparatus according to claim 9 wherein said odometer means furtherincludes a stepping motor for providing said odometer indication inaccordance with said dividing circuit means output signal.
 11. Anapparatus according to claim 10 wherein said odometer means includesdriving circuit means receiving said dividing circuit means outputsignal for providing electrical pulses to said stepping motor meanswhich provide one rotational step of said stepping motor upon one outputpulse of said driving circuit means.
 12. For a vehicle having a wheelwith a tire of a predetermined size; an apparatus for indicating vehiclespeed and the distance traveled by the vehicle comprising: a sensorproviding a predetermined number of pulses for each rotation of thevehicle wheel regardless of tire size so that the frequency of saidsignal is representative of the rate of rotation of the vehicle wheel;speed indicating means responsive to said sensor signal for providing aspeed indication; odometer means including frequency dividing circuitmeans responsive to said sensor signal for providing an output signalhaving a frequency representative of said sensor signal frequencydivided by a quotient, said odometer means utilizing said dividingcircuit means to provide an indication of the distance traveled by thevehicle, and calibrating means receiving means operatively associatedwith each of said speed indicating means and said odometer means; andunitary calibrating means being interchangeably received by saidcalibrating means receiving means for calibrating both said speedindicating means and said odometer means in accordance with saidpredetermined tire size, said unitary calibrating means includingspeedometer calibrating means for establishing the responsiveness ofsaid speed indicating means to said sensor signal and odometercalibrating means for changing said quotient of said frequency dividingcircuit means.
 13. An apparatus according to claim 12 wherein saidspeedometer calibrating means includes a resistor adapted to establishthe responsiveness of said speed indicating means to said sensor signal.14. An apparatus according to claim 13 wherein said indicating means isa meter with said resistor in a circuit for said meter establishing theresponsiveness thereof.
 15. An apparatus according to claim 12 whereinsaid calibrating means is a program for said apparatus.
 16. An apparatusaccording to claim 21 wherein said program is in the form of a circuitfor establishing preselected circuit connections with said meansoperatively associated with said indicating means for establishing theresponsiveness of said indicating means to said sensor signal inaccordance with said program.
 17. An apparatus according to claim 12wherein said means operatively asSociated with said indicating meansincludes a circuit for receiving pulses representative of the rotationof said vehicle wheel which is adapted to provide output pulses whichare representative of the input pulses divided by a divisor, saidcircuit being programmable to establish said divisor in accordance withthe size of said tire, said indication being in accordance with saidprogrammable circuit output pulses.
 18. An apparatus according to claim17 wherein said calibrating means is a program in the form of a circuithaving preselected circuit connections adapted to be operationallycooperative with said programmable circuit for establishing saiddivisor.